Magnetic sensor device

• US 6,566,872 B1
• Filed: 12/31/2001
• Issued: 05/20/2003
• Est. Priority Date: 12/31/2001
• Status: Expired due to Fees

• Current Assignee: Novuyoshi Sugitani
• Original Assignee: Xenosensors, Inc.
• Inventors: Sugitani, Novuyosi
• Primary Examiner(s): Lefkowitz, Edward
• Assistant Examiner(s): Zaveri, Subhash
• Application Number:
  US10/029,870
• Time in Patent Office: 505 Days
• Field of Search: 324/249, 324/244, 324/260, 324/259, 324/236, 324/252, 360/110, 360/125
• US Class Current: 324/249
• CPC Class Codes: G01R 33/02 Measuring direction or magnitude of magnetic fields or magnetic flux G01R33/20 takes precedence
• CPC Class Codes: G11B 2005/0005 Arrangements, methods or circuits
• CPC Class Codes: G11B 5/332 using thin films G11B5/372, G11B5/3903 take precedence

Abstract

A magnetic sensor device has a magnetic sensor having a magnetic material whose threshold frequency is changed by a magnetic field to be detected, and the device has the so-called electromagnetically-coupled current path which is affected by the magnetic material in order to electrically detect the threshold frequency of the magnetic material. The current path is connected to an oscillator circuit, which is set so that its oscillation frequency is changed by a change in the threshold frequency of the magnetic sensor. In the magnetic sensor device, the magnetic field to be detected causes a change in the oscillation frequency of the oscillator circuit, and the change in the frequency is extracted as a magnetic field detection signal. More specifically, a change in the threshold frequency of the magnetic material of the magnetic sensor caused by the magnetic field to be detected is extracted as a change in an output frequency of the oscillator circuit, and the change in the output frequency is used as the magnetic field detection signal.

Claims

1. A magnetic sensor device comprising:

a magnetic material to which a magnetic field to be detected is applied; and

oscillating means for oscillating in a threshold frequency range of said magnetic material,

wherein said oscillating means oscillates in a transient threshold frequency range in which a loss component that is an imaginary part of complex magnetic permeability of said magnetic material increases and effective magnetic permeability that is a real part of the complex magnetic permeability decreases sharply, thereby detecting a change in the magnetic field to be detected as a change in an oscillation frequency in the threshold frequency range.

2. The magnetic sensor device according to claim 1, wherein the threshold frequency range of said magnetic material is near a magnetic resonance frequency of said magnetic material.

10. The magnetic sensor device according to claim 1, wherein the magnetic field to be detected is a magnetic storage pattern stored through magnetization.

11. The magnetic sensor device according to claim 1, wherein the magnetic field to be detected is a magnetic field generated by an electric signal generated by a coil.

3. A magnetic sensor device comprising:

a magnetic material; and

an oscillator circuit which sets an oscillation frequency to a frequency near a threshold frequency of said magnetic material and oscillates at the set oscillation frequency,

wherein said oscillator circuit detects a change in the threshold frequency of said magnetic material caused by a change in a magnetic field to be detected as a change in the oscillation frequency of said oscillator circuit, and outputs the change in the magnetic field to be detected as the change in the oscillation frequency.

4. The magnetic sensor device according to claim 3, wherein said magnetic material is included in a magnetic sensor, the magnetic sensor has a conductor which lets a current of said oscillator circuit pass through, as well as said magnetic material, and said magnetic material has much higher volume resistivity than the conductor has.

5. The magnetic sensor device according to claim 3, wherein said magnetic material is included in a magnetic sensor, and the magnetic sensor has said magnetic material, an electrical insulating layer, and a conductor which is located with the electrical insulating layer in between the conductor and said magnetic material, is affected by the threshold frequency of said magnetic material and lets a current of said oscillator circuit pass through.

6. The magnetic sensor device according to claim 5, wherein at least said magnetic material of the magnetic sensor is formed as a thin film magnetic film by use of thin film process.

7. The magnetic sensor device according to claim 6, wherein the magnetic film is formed of a multilayer film comprising a magnetic layer and a nonmagnetic layer, which are stacked.

8. The magnetic sensor device according to claim 5, wherein said oscillator circuit is formed on a semiconductor substrate on which the magnetic sensor is formed.

9. The magnetic sensor device according to claim 8, wherein a bias magnetic field generator for applying a bias magnetic field to the magnetic sensor is provided near the magnetic sensor.

12. A magnetic sensor device comprising:

a thin film magnetic sensor including a conductive layer and a thin film magnetic film; and

an oscillator circuit connected to the conductive layer of said thin film magnetic sensor, said oscillator circuit which sets an oscillation frequency to a frequency near a magnetic resonance frequency of the magnetic film and oscillates at the set oscillation frequency,

wherein said oscillator circuit detects a change in the magnetic resonance frequency of the magnetic film caused by a change in a magnetic field to be detected as a change in the oscillation frequency of said oscillator circuit, and outputs the change in the magnetic field to be detected as the change in the oscillation frequency.